Utilization of fine mineral matter in the conversion of non-biodegradable plastic and in remediation of soils polluted with non-biodegradable plastic

ABSTRACT

The disclosed invention describes a novel approach to the utilization of the fine mineral matter derived from coal and/or coal refuse (a by-product of coal refining) to convert a non-biodegradable plastic into a biodegradable plastic. The fine mineral matter could also be based on volcanic basalt, glacial rock dust deposits, iron potassium silicate and other sea shore mined deposits. The conversion of the non-biodegradable plastic into biodegradable plastic in soil further increases nutrients availability in soil with the transition metals released as a result of biodegradation of the biodegradable plastic.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/647,818, filed Mar. 25, 2018, the contents of which are incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The invention generally relates to the conversion of a non-biodegradableplastic into a biodegradable plastic. More specifically, in oneembodiment, a method for remediation and treatment of soil using thebiodegradable plastic is described.

BACKGROUND OF THE INVENTION

Polyolefin Based Plastic Products in Soil

Over the past 60 years, agricultural output and productivity hassignificantly increased and plastic materials, mainly polyolefins (e.g.low density polyethylene (LDPE), high density polyethylene (HDPE),linear low density polyethylene (LLDPE), polypropylene (PP), and theircopolymers and mixtures) made substantial contribution to thisdevelopment. The main products based on polyolefins are films,drip-irrigation tubing and tapes. For the mulch film alone, it isestimated that about 1 million tons is used worldwide on over 30 millionacres of land (P. Halley at al. “Starch” published in 2001 (53), page362-367). For the USA these numbers in 2004 corresponded to about of130,000 tons of mulch film usage annually, covering over 185,000 acresof agricultural land (J. P. Warnick at al. “Renewable Agriculture andFood Systems” published in 2006 (21), 216-233). These numbers havecontinued to grow significantly due to the benefits of mulch films suchas increased soil temperature, reduced weed growth, moistureconservation, reduction of certain insect pests, higher crop yields, andmore efficient use of soil nutrients.

One major drawback of polyolefins is their resistance to chemical,physical and biological degradation, along with the problem of removaland disposal of agricultural films and other agricultural products aftertheir useful lifetime. If not removed, they tend to accumulate as waste,interfere with root development of the subsequent crop and createserious environmental problems. The cost of removing films from the soiland cleaning them is prohibitively high. This is the main reason why thefarmers usually incorporate them into the soil by rototilling, orsometimes burn them in the fields. The problems with disposal ofagricultural plastic waste and soil contamination with plastic wastebecome more and more severe because of increasing usage of plastics.

It is also known that since 2004 well over 1.5 million tons of plastic(primarily polyolefins) mulch film was used in USA. With thesepractices, it is expected that significant amounts of these plastics areaccumulated in soil as waste. It is also known that soils polluted withplastic lose their agricultural value and need to be remediatedregularly.

A possible solution to the agricultural plastic waste management wouldbe deployment of biodegradable materials. Biodegradability could beachieved by utilization of soil biodegradable polymers, such ashydrolysable polyesters, e.g. poly(hydroxyalkanoates) (PHA),poly(butylene succinates) and their copolymers. However, despite manyyears of research and development, these polymers still did not makesignificant impact in the marketplace due to their inconsistent soilbiodegradability and in a majority of cases the necessity of removal andcompositing, high cost, life cycle assessment (LCA) and inferiormechanical properties.

A far more promising solution lies in converting polyolefins, thepolymers of choice for agricultural film markets, into biodegradablematerials that further enriches the agricultural soil with nutrients.This is a quite an ambitious task as polyolefins are known to bebioinert due to their hydrophobicity and high molecular weights.

Transition Metals as Soil Nutrients

Transition metal salts and their mixtures are known to be importantplant nutrients: iron, copper, zinc, molybdenum, among others, areneeded to support photosynthesis, tolerance to biotic and abiotic stressor nitrogen fixation. However, plants often grow in soils with limitedbioavailability (especially of metals in reduced form) and thereforerely on microorganisms for metal uptake. The U.S. Publication. No.20160311728A1 teaches that coal-derived mineral matter mixed with soilis an effective soil amendment. It increases the silt and clay fractionsof the soils and improves soil texture. However, it fails to provide asolution for the soils polluted with non-biodegradable waste.

SUMMARY OF THE INVENTION

An object of the present invention is to utilize fine mineral matter toconvert a non-biodegradable plastic into a biodegradable plastic. Thefine mineral matter is either derived from coal refuse and/or fine-sizecoal or mined from natural resources including volcanic basalt, glacialdust deposits, iron potassium silicate and/or sea shore deposits.

Yet another object of the present invention is to improve the soilquality by converting a non-biodegradable plastic in soil into abiodegradable plastic.

Yet another object of the present invention is treatment of the soil byadding the biodegradable plastic-based product comprising thenon-biodegradable plastic-based product mixed with the fine mineralmatter such that the biodegradable plastic-based product releases aplurality of transition metals.

Yet another object of the present invention is to provide abiodegradable polyolefin composition that biotically degrades in theenvironment without having adverse effects.

Yet another object of the present invention is to provide a modifiedsoil composition comprising a biodegradable plastic with increasedamount of nutrients and improved fertility.

Yet another object of the present invention is the beneficial use of thecoal derived fine mineral matter otherwise accumulating as refuse andrequiring disposal, and in supporting clean air practices supporting theseparation of fine coal fractions otherwise producing fly ash and airpollutants if the coal is burned in a power plant.

In an embodiment of the present invention, the fine mineral matter iseither derived from coal refuse and/or fine-size coal with frothflotation separation or mined from natural resources including volcanicbasalt, glacial dust deposits, iron potassium silicate and/or sea shoredeposits with particle sizes ranging from less than about 50 μm to about2 μm.

In another embodiment of the present invention, a method of conversionof a non-biodegradable plastic into a biodegradable plastic isdescribed. The method comprises the steps of obtaining an amount of finemineral matter and blending (melt blending, dry blending or compounding)the fine mineral matter with the non-biodegradable plastic, therebyconverting the non-biodegradable plastic into the biodegradable plastic.

In another embodiment of the present invention the non-biodegradableplastic to be converted is a polyolefin-based plastic such as LDPE,HDPE, LLDPE, PP and their copolymers and mixtures. In an alternativeembodiment, the non-biodegradable plastic is a hydrocarbon-based polymerfrom the list which includes, but is not limited to, polybutenes,polymethylpentenes, polystyrene, styrene/acrylonitlrile copolymers,acrylonitrile/butadiene/styrene terpolymers,acrylate/styrene/acrylonitrile terpolymers, sterene/butadiene/styreneand styrene/isoprene/styrene copolymers, acrylic, vinyl based polymers,polycarbonates, and their mixtures and copolymers. In addition,polyesters, polyethers, polyether esters, polyurethanes, andpolyacetals, polyisoprene, polybutadiene are included in the list.

In another embodiment of the present invention, a method of conversionof a non-biodegradable plastic in soil into a biodegradable plastic isdescribed. The method comprises the steps of obtaining an amount of finemineral matter and blending (melt blending, dry blending or compounding)the fine mineral matter with soil comprising the non-biodegradableplastic to convert the non-biodegradable plastic in soil into thebiodegradable plastic.

In another embodiment of the present invention, a biodegradablepolyolefin composition comprises a non-biodegradable polyolefin-basedproduct and an amount of fine mineral matter, wherein thenon-biodegradable polyolefin-based product is blended (melt blending,dry blending or compounding) with the fine mineral matter.

In another embodiment of the present invention, a modified soilcomposition comprises a non-biodegradable polyolefin and an amount offine mineral matter, wherein the non-biodegradable polyolefin isconverted into a biodegradable polyolefin when melt blending, dryblending or compounding with the fine mineral matter.

In another embodiment of the present invention, a method for treatmentof soil is described. The method comprises the steps of adding abiodegradable plastic-based product (formed by blending an amount offine mineral matter and a non-biodegradable plastic-based product) inthe soil. The biodegradable plastic-based product releases a pluralityof transition metals to increase nutrient availability in the soil.

In another embodiment of the present invention, a method for remediationof soil is described. The method comprises the steps of obtaining anamount of fine mineral matter comprising a plurality of transitionmetals, and mixing the fine mineral matter with soil to form a blend,wherein the soils comprises a non-biodegradable plastic-based product.The plurality of transition metals causes the oxidative degradation ofthe non-biodegradable plastic-based product present in the blend to forma biodegradable plastic-based product. The biodegradable plastic-basedproduct formed releases the plurality of transition metals to increasenutrient availability in the soil.

From the foregoing disclosure and the following more detaileddescription of various embodiments, it will be apparent to those skilledin the art that the present invention provides a way to utilize finemineral matter to convert non-biodegradable plastic into biodegradableplastic. Particularly significant in this regard is the potential theinvention affords for providing a relatively simple, low cost andefficient conversion of non-biodegradable plastic into biodegradableplastic. Additional features and advantages of various embodiments willbe better understood in view of the detailed description provided below.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 represents a flow diagram illustrating the method of conversionof the non-biodegradable plastic into biodegradable plastic according toan embodiment of the invention.

FIG. 2 represents a flow diagram illustrating the method of conversionof non-biodegradable plastic in soil into biodegradable plasticaccording to another embodiment of the invention.

FIG. 3 represents a flow diagram illustrating the method of treatment ofsoil according to another embodiment of the invention.

FIG. 4 represents a flow diagram illustrating the method for remediationof soil according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description represents the best currentlycontemplated techniques for carrying out the invention. The descriptionherein is not limiting, but rather is made merely for the purpose ofillustrating the general principles of the invention.

A non-biodegradable plastic can be made biodegradable via an oxidativedegradation process catalyzed in the presence of light, heat orpro-degrading additives. During this oxidative degradation the molecularchains of non-biodegradable plastic are reduced by oxidation, creatingcarboxylic acids, alcohols and ketones. The originally hydrophobicmacromolecules become more hydrophilic and favour extracellular enzymeactivity leading to subsequent breakdown of polymer chains (see e.g., N.C. Billingham, E. Chiellini, A. Corti, R. Baciu and D. W. Wiles, inENVIRONMENTALLY DEGRADABLE PLASTICS BASED ON OXO-BIODEGRADATION OFCONVENTIONAL POLYOLEFINS, Springer US 2003). The pro-degrading additivesused for oxidative degradation contain different mixtures of transitionmetal salts (e.g., iron, copper, nickel, cobalt, zinc, manganese,titanium, zirconium, molybdenum), with or without alkaline earth salts(e.g., calcium, magnesium) and with or without the presence of otheringredients such as substituted benzophenones, unsaturated organiccompounds, peroxides, biodegradable plasticizers, waxes, etc.

The present invention utilizes the fine mineral matter to convert thenon-biodegradable plastic into biodegradable plastic in a preferredembodiment. The fine mineral matter is derived from coal and/or minedfrom natural resources, such as volcanic basalt, glacial rock dustdeposits, iron potassium silicate and other sea shore deposits. Thenon-biodegradable plastic is completely degraded and converted intobiodegradable plastic due to oxidative degradation of non-biodegradableplastic caused by the transition metals present in the fine mineralmatter and other additives participating in electron exchange andregeneration of reduced ions of transition metals. The biodegradableplastic undergoes biodegradation to remediate and treat the soil,thereby improving the texture and increasing the nutrients availability.

Fine Mineral Matter Derived from Coal

Coal comprises low-quality coal mixed with fine mineral mattercontaining a plurality of elements, among them transition metalcompounds such as Fe, Cu, Mn, Mo, Zn, Co and alkali/alkali earth metalssuch as K, Ca, Mg. The residual fine mineral matter is discarded as a“waste” after coal cleaning processes and ends up either fillingravines, streams, mountain hollows or is randomly disposed in piles nearthe mine sites.

Another source of deriving fine mineral matter is its separation duringrecovery of coal refuse. It is known that about 1 billion tons of coalrefuse is discarded each year.

The fine mineral matter inherent in coal refuse or fine-size coal isseparated with froth flotation with particle sizes ranging from lessthan about 50 μm to about 2 μm. The separation process separatesfine-size coal particles by selective attachment of air bubbles to coalparticles, causing them to be buoyed to the surface of a coal-watersuspension system where they are collected in a froth. Since finemineral matter particles remain unattached, they are not recovered inthe froth and are present in the tailing or the underflow. The finemineral matter is recovered when the flotation cell is drained. Thisprocess deals with fine particles in a turbulent, aqueous system wherespecific gravity is not as significant as the surface properties of theparticles. This is one of the principal processes used for cleaningfine-sized coal, however other suitable techniques can also be used.

The concentration of metals and metal salts depends on the analyticalmethod being used and is typically measured by X-ray techniques:fluorescence (XRF) and diffraction (XRD) and Inductively Coupled PlasmaAcid Elemental Analysis (ICP-AES). The X-ray methods are non-destructiveand determine the elemental composition of materials in bulk. The ICPmethods require digestion of minerals in either strong acids to estimatethe concentration of elements that could potentially become“environmentally available” (ICP-AES) or in milder dissolution solventsto provide more realistic soil availability. The elements bound insilicate structures, e.g., are not normally dissolved by theseprocedures, as they are not usually mobile in the environment. Thistechnique is generally used to show compliance in EPA 503 heavy metalregulations.

The concentration of the transition metals and the alkali/alkali earthmetals in the coal refuse varies for different coal sites and arepresented in the Table 1 below. The concentrations measured are based onthe ICP-AES method utilizing nitric acid, hydrochloric acid and hydrogenperoxide in a heated digester. The compositions of different refuseswere shown to differ, but all had Iron as the major element, and therest of the elements were also present in each refuse. Table 1 confirmsthat the concentration of toxic and regulated heavy metals is belowregulatory limits, which are also provided.

TABLE 1 Fine mineral matter ICP-AES and WDXRF tests. EN EPA 40 CRF Part503 in soil 17033: Bio 2018 Solids Sludge Coal derived Upper UpperAnnual fine mineral matter limit limit Max loading Cumulative WDXRFICP-AES, ICP, ICP, concen. rates, loading ppm ppm ppm ppm ppm lb/A/yrrates, lb/A Elements In bulk Strong digestion Aluminum 15,200-15,700Arsenic <20  5-11 <41 <75 1.8 36.6 Barium 300-500 Beryllium 0.9-1.1Boron  5-17 Cadmium   0-0.32 <0.5 <39 <85 1.7 34.8 Calcium  8,590-17,000Chloride  23-304 Chromium 14-28 <50 <1,200 3,000 134 2,679 Cobalt  8-12<20 Copper 23-43 <50 <1,500 4,300 67 1,340 Fluoride  3-5.6 Iron18,900-30,100 Lead 20 14-20 <50 <300 420 14 375 Magnesium 4,780-5,190Manganese 193-253 5,500 Mercury  0.06-0.068 <0.5 <17 840 13.4 268Molybdenum   1-1.93 <18 57 0.8 15 Nickel <11 <25 <420 75 0.8 16 Niobium28 Phosphorus 139-203 Potassium  2000-2,980 Rubidium 150 Selenium ND*<36 100 4 89 Silicon 453-716 Silver ND* Sodium  386-1000 Strontium279-374 Sulfur 1,920-3,300 Thorium 20 Tin <50 ND* Tungsten <10 Uranium<20 Vanadium 130 13-16 Yttrium 40-45 <100 Zinc 71-83 <150 <2,800 7,500125 2,500 *ND = Not DetectableFine Mineral Matter from Other Naturally Occurring Sources

Other fine mineral matter could be based on volcanic ash deposits minedin Utah and sold under the trade name Azomite. It is marketed asmineralized soil fertilizer, but also includes transition metals in itscomposition and is approved for organic farming.

Another example of fine mineral matter could be based on volcanicbasalt, e.g., a product mined by Cascade Minerals. It is also used forsoil mineralization and is approved for organic farming.

Another example of fine mineral matter could be based on glacial rockdust deposits, e.g., glacial rock dust deposits sold by Gaia GreenProduct Ltd.

Another example is iron potassium silicate, containing 20% iron oxideFeO2, e.g., products supplied by Gaia Green Product Ltd based on ancientalgae sea shore mined deposits.

Conversion of Non-Biodegradable Plastics into Biodegradable Plastics byUtilization of Fine Mineral Matter

In the preferred embodiment of the present invention shown in FIG. 1, aflow diagram 1 of a method of conversion of a non-biodegradable plasticinto the biodegradable plastic is described. The non-biodegradableplastic to be converted is a polyolefin-based plastic such as LDPE,HDPE, LLDPE, PP and their copolymers and mixtures. In an alternativeembodiment, the non-biodegradable plastic is a hydrocarbon based polymerfrom the list which includes, but is not limited to polybutenes,polymethylpentenes, polystyrene, styrene/acrylonitlrile copolymers,acrylonitrile/butadiene/styrene terpolymers,acrylate/styrene/acrylonitrile terpolymers, sterene/butadiene/styreneand styrene/isoprene/styrene copolymers, acrylic, vinyl based polymers,polycarbonates, and their mixtures and copolymers. In addition,polyesters, polyethers, polyether esters, polyurethanes, and polyacetalsare included in the list.

The method of conversion illustrated in flow diagram 1 and as shown inFIG. 1 begins with S1 where an amount of fine mineral matter isobtained. The fine mineral matter is separated from the coal refuseand/or fine-size coal with the froth flotation separation processdescribed above. The fine mineral matter could also be mined fromnatural sources, such as volcanic basalt, glacial rock dust deposits,iron potassium silicate and other sea shore mined deposits. The particlesize of the fine mineral matter ranges from less than about 50 μm toabout 2 μm. The fine mineral matter comprises at least one and morepreferably at least two transition metals selected from the groupconsisting of Fe, Cu, Mn, Mo, Zn, Co, or combinations thereof to causethe oxidative degradation of the non-biodegradable plastic. Thesetransition metals in the fine mineral matter have concentrationsmeasured with ICP-AES method utilizing nitric acid, hydrochloric acidand hydrogen peroxide in a heated digester and are defined in the rangeshown in Table 2.

TABLE 2 Concentration range of the transition metals in the fine mineralmatter. Transition Concentrations Metal Range in ppm Fe 14,000-45,000 Cu10-50 Mn 100-700 Mo 1-2 Zn  20-120 Co 10-15

The fine mineral matter further comprises a promoter from the list ofCa, K, Mg or combinations thereof, to promote the oxidative degradationof the non-biodegradable plastic. The promoter in the fine mineralmatter has concentrations defined in the range shown in Table 3. Otheralkaline/alkaline earth containing minerals with similar fractions ofsoluble cations can also be used as promoters for oxidative degradation.

TABLE 3 Concentration range of the promoter in the fine mineral matter.Promoter Concentrations (Alkali/Alkali Range Earth Metal) in ppm Ca 1,000-18,000 K   600-4,000 Mg   20-8,000

In step S2, the fine mineral matter is melt blended, dry blended, orcompounded with the non-biodegradable plastic. The fine mineral matteris added to the non-biodegradable plastic directly or via masterbatchesor concentrates, wherein the masterbatches or concentrates arewell-dispersed mixtures of a polymer and high percentages of one or morecomponents (e.g., fine mineral matter and additives) in knownproportions for use in blending in appropriate amounts with the basicpolymer in the preparation of a compound. Masterbatches or concentratescan be prepared by any known melt blending techniques, preferablyextrusion. Single or twin screw extruders with different L: D (length todiameter) ratios can be used. The concentrations of the fine mineralmatter in the masterbatches are believed to be in the range of about 3to about 50 wt. %. The concentration of the fine mineral matter in thenon-biodegradable plastic is determined by at least one of the factorscomprising, composition of the transition metals, specifics of thenon-biodegradable plastic resin, climatic conditions and desired usefullifetime of the formulated biodegradable plastic.

In step S3, the non-biodegradable plastic undergoes oxidativedegradation abiotically. The transition metals in the fine mineralmatter catalyze oxidative degradation and conversion of thenon-biodegradable plastic into the biodegradable plastic. In case ofpolyolefins and other hydrocarbon-based polymers sensitive to radicalchain processes, the rate-determining part of the degradation process isthe oxidation segment, commonly called peroxidation. Hydrocarbonpolymers vary in their ability to resist (or undergo) peroxidation.Thus, the oxidative stability increases from natural rubber(cis-poly(isoprene)) to poly(butylene) to polypropylene to polyethyleneto polyvinyl chloride. Within polyethylenes, due to their chemical andmorphological characteristics, LDPE and LLDPE are more susceptible tooxidative degradation than HDPE.

Abiotic peroxidation of the polyolefins produces vicinal hydroperoxides.This process is particularly favored in poly-α-olefins, such aspolypropylene due to the susceptibility of the tertiary carbon atom tohydrogen abstraction. The vicinal hydroperoxides are unstable and can beconverted to free radicals under heat and/or UV light. These radicals inturn initiate new oxidation chains. Since the monomolecular hemolyticdecomposition of hydroperoxide groups into free radicals requiresrelatively high activation energies, this process becomes effective onlyat temperatures in the range of 120° C. However, in the presence ofcatalytic amounts of transition metal ions, hydroperoxides decompose atroom temperature by a redox mechanism shown in the Reactions 1 below.

These free radicals enter a chain reaction with oxygen and C—H bonds inthe non-biodegradable plastic to yield a range of oxidation products.The extent of oxidative degradation of non-biodegradable plastic (allabove mentioned polymers) strongly depends on the number of otherfactors, including their composition, purity, and glass transitiontemperature.

The challenge in designing fully biodegradable systems based onpolyolefins is in driving their oxidative degradation to the point whentheir structure is transformed from hydrophobic to hydrophilic and theirmolecular weight reduced to <20,000 or <15,000 g/mol. To supportcontinuous oxidative degradation and transformation of non-biodegradableplastic it is essential to enable regeneration of reduced transitionmetals ions when they are used to accelerate the oxidative degradationprocess. Such regeneration can be driven by the redox reactions duringthe catalytic degradation and by providing the best conditions topromote recurring reactions. It is known that Fe³⁺ is thethermodynamically favored oxidation state for iron under aerobic andalkaline conditions, whereas Fe²⁺ is favored under anaerobic and acidicconditions. The present invention uses catalytic systems enabling theelectron transfer and regeneration of reduced ions of transition metals,which would catalyze decomposition of the hydroperoxide groups into freeradicals and consequently decomposing non-biodegradable plastic polymersaccording to Reactions 1 above. For that purpose the catalytic systems,in addition to containing multiple transition metal ions, also containaccelerators of redox reactions. To facilitate conversion of Fe²⁺ intoFe³⁺ carboxylic acids such as steric acids can be used according toReactions 2 below.

Reactions 2, where “P” is a polymer chain,Fe²⁺+H₃₅C₁₈-COOH+POO.→Fe³⁺+H₃₅C₁₈-COO⁻+POOH,

The acid accelerators could be other known carboxylic acids such aspalmic acid, lauric acid, arachidic acid, nonadecylic acid, myristicacid, capric acid, valeric acid, caproic acid, butyric acid and aminoacids.

-   -   Unsaturated (including polyunsaturated) carboxylic acids such as        oleic, palmitoleic, vaccenic, linoleic, arachidonic, nervonic,        stearidonic, erucic, rumenic, pinolenic, etc would be strongly        preferred    -   Dicarboxylic acids, tricarboxylic acids, alpha hydroxyl acids,        divinylether fatty acids could be other examples of accelerators

To facilitate regeneration of Fe²⁺, amine compounds can be usedaccording to Reactions 3:

Reactions 3Fe³⁺+H₃₅C₁₈-NH₂+HO⁻→Fe²⁺+H₃₅C₁₈—NH.+H₂OH₃₅C₁₈—NH.+H.→H₃₅C₁₈—NH₂

The amine accelerators could be monomeric aliphatic amines, e.g. stearylamine, or polymer-based amines, e.g. [(3-(11-aminoundecanoyl) amino)propane-1-] silsesquioxane (polyhedral oligomeric silsesquioxane, POSS),and chitosan. They could be more preferred due to their lower leakagepotential from polyethylene (due to its structure and molecular weight).

Additionally, the fine mineral matter contains other additives selectedfrom antioxidants, pigments, IR absorbers, lubricants, unsaturatedorganic compounds, substituted benzophenones, peroxides, biodegradableplasticizers, waxes, UV and thermal stabilizers, biodegradable polymersand oligomers, or combinations thereof. Additives in combination withtransition metals promote their ability to decompose hydroperoxides andform free radicals.

In order to control both the lifetime of a biodegradable plastic duringuse as well as the rate of subsequent biodegradation in the environment,the onset of degradation must be controlled by appropriate antioxidants.Antioxidants are used to inhibit oxidative degradation of plastics toprovide required initial properties of plastic materials. Because thepresent invention uses transition metal ions to catalyze thedecomposition of hydroperoxides, the utilization of primary antioxidantsto control the onset of oxidative degradation would be the mostpreferred option. Primary antioxidants stabilize free radicals,especially peroxyl radicals, (POO.) by donating hydrogen (H), thuspreventing formation of new alkyl radicals (P.) via abstraction of ahydrogen from a nearby polymer chain. The action of primary antioxidantsreduces but does not prevent degradation. This in turn leads toaccumulation of hydroperoxides, which after the consumption of primaryantioxidants are going to be decomposed by transition metal ions at theenvironmental conditions. The secondary antioxidants, which arechemically reducing hydroperoxides would be less preferred (e.g.phosphites, thioesters).

Finally, in step S4, the non-biodegradable plastic is converted into thebiodegradable plastic. Potential concentrations of the fine mineralmatter in final products are from about 0.1 to about 3 wt. %.

According to this invention, conversion of non-biodegradable plasticinto biodegradable plastic can take place in the fresh water or marineenvironment. The floating in water plastics, such as but not limited topolyolefins (polyethylenes, polypropylene, their copolymers,polymethylpentene, polybutene, etc), natural rubber, nylons,acrylonitrile butadiene styrene copolymers, polystyrene, would besubjected to UV light almost at all times and would go through theabiotic degradation by described above mechanisms. J.-F. Ghiglione, inhis response to the Eunomia Report also describes the presence of thespecific bacteria such as Alcanivorax borkumensis and R. rhodochrouswhich are ubiquitous in the oceans and able to biodegrade hydrocarbons.The population of such microorganisms is known to increase in responseto increased availability of a food source, e.g. oil spills. Thechemical break down of the polymeric molecules and their increasinghydrophilicity would also prevent ocean pollutants such as PCBs(polychlorinated biphenyls) adsorb onto the plastic surface, which is aknown problem with non-biodegradable plastics.

In another embodiment of the present invention shown in FIG. 2, a flowdiagram 2 of a method of conversion of a non-biodegradable plastic insoil into a biodegradable plastic is described. The operating conditionsare identical to those of the preferred embodiment.

The method of conversion illustrated in flow diagram 2 and as shown inFIG. 2 starts with step S11 where an amount of fine mineral matterranging from less than about 50 μm to about 2 μm is obtained. Theconcentration of the transition metals in the fine mineral matter isdefined in the range shown in the Table 2 above of the presentinvention. The fine mineral matter comprises a transition metal from thegroup consisting of Fe, Cu, Mn, Mo, Zn, Co, or combinations thereof tocause the oxidative degradation of the non-biodegradable plastic.

The fine mineral matter further comprises a promoter from the groupconsisting of Ca, K, Mg, or combinations thereof with concentrationsdefined in the Table 3 above of the present invention.

In step S12, the fine mineral matter is melt-blended, dry blended orcompounded comprising a non-biodegradable plastic. The fine mineralmatter is added to the soil directly or via masterbatches orconcentrates to achieve well-dispersed mixtures. Further, about 10 to 30wt. % of fine mineral matter would be needed to be blended with thenon-biodegradable plastics present in soil. The concentration of thefine mineral matter in the soil is determined by at least one of thefactors comprising composition of the transition metals, specifics ofthe non-biodegradable plastic resin, climatic conditions and desireduseful lifetime of the formulated biodegradable plastic. The blendingcan be done with a rototiller to achieve a homogeneous dispersion. A fewrototilling soil treatments are recommended to promote better dispersionof the fine mineral matter in soil.

In step S13, the non-biodegradable plastic in soil undergoes oxidativedegradation. The transition metals in the fine mineral matter togetherwith other promoters, such as carboxylic acids and primary amine basedcompounds and alkaline and alkaline earth metals act as a catalystpromoting redox reactions and leading to oxidative degradation of thenon-biodegradable plastic to convert the non-biodegradable plastic intothe biodegradable plastic according to Reactions 1, Reactions 2 andReactions 3 of the present invention described above. The promoters inthe fine mineral matter further promote the oxidative degradation of thenon-biodegradable plastic into the biodegradable plastic in soil.

Finally, in step S14, the non-biodegradable plastic is converted intothe biodegradable plastic in soil. Potential concentrations of the finematter in the final products are from about 0.1 to about 3 wt. %.

In another embodiment of the present invention, a biodegradablepolyolefin composition is described. The biodegradable polyolefincomposition comprises a non-biodegradable polyolefin-based product andan amount of fine mineral matter, wherein the non-biodegradablepolyolefin-based product is melt-blended, dry blended or compounded withthe fine mineral matter with particle size ranging from less than about50 μm to about 2 μm. The concentration of the fine mineral matter in thenon-biodegradable polyolefin-based product is determined by at least oneof the factors comprising composition of the transition metals,specifics of the non-biodegradable plastic resin present in soil,climatic conditions and desired useful lifetime of the formulatedbiodegradable polyolefin. A transition metal from the group consistingof Fe, Cu, Mn, Mo, Zn, Co, or combinations thereof present in the finemineral matter act as pro-oxidants and cause oxidative degradation ofthe non-biodegradable polyolefin-based product. The transition metals inthe fine mineral matter have concentrations defined in the range shownin the Table 2 above of the present invention. The oxidative degradationconverts the non-biodegradable polyolefin-based product into abiodegradable polyolefin composition according to the Reactions 1,Reactions 2 and Reactions 3 of the present invention described above.

In another embodiment of the present invention, a modified soilcomposition comprises a non-biodegradable polyolefin and an amount ofthe fine mineral matter with particle sizes ranging from less than about50 μm to about 2 μm, wherein the fine mineral matter is melt-blended,dry blended or compounded with the non-biodegradable polyolefin presentin the soil. The non-biodegradable polyolefin is converted into abiodegradable polyolefin when blended with the fine mineral matter. Thefine mineral matter is added to the soil directly. It is believed thatabout 10 to about 30 wt. % of fine mineral matter would be needed to beblended with the non-biodegradable plastics present in soil. The finemineral matter comprises the transition metal from the group consistingof Fe, Cu, Mn, Mo, Zn, Co, or combinations thereof. The transitionmetals in the fine mineral matter have concentrations defined in therange shown in the Table 2 of the present invention. The transitionmetals act as pro-oxidants and cause the oxidative degradation of thenon-biodegradable polyolefin present in soil according to the Reactions1, Reactions 2 and Reactions 3 of the present invention described above.As a result of this oxidative degradation, the non-biodegradablepolyolefin gets converted into the biodegradable polyolefin to form amodified soil.

Soil Treatment and Soil Remediation with Biodegradable Plastic

The fine mineral matter containing transition metals provides soilnutrition, recovers the soil fertility and conditions the soil. The soilanalysis data based on ICP using milder dissolution solvents (simulatingsoil conditions for metal salt dissolution) with reference to Table 4,confirms the presence of following plant nutrients:

TABLE 4 ICP digestion solvents strong acids buffered buffered ICP AESICP ICP Phosphorus (P2O5), 256 2.8 13.7 ppm Potassium, ppm 3,298 80.591.4 Magnesium, ppm 4,734 225 268 Calcium, ppm 9,420 1,693 1,473 Sodium,ppm 882 254 135 Sulfur SO4, ppm 3,214 247 134 Zinc, ppm 72 24 4.9Manganese, ppm 191 5 12 Iron, ppm 17,488 25 339 Copper, ppm 37 35 26

In another embodiment of the present invention shown in FIG. 3, a flowdiagram 3 of a method for treatment of soil is described. Abiodegradable plastic-based product is added in the soil. Thebiodegradable plastic-based product undergoes biodegradation to treatthe soil. The operating conditions are identical to those of thepreferred embodiment.

The method of treatment illustrated in flow diagram 3 and as shown inFIG. 3 starts with step S21 where a biodegradable plastic-based productis added in the soil formed by melt blending, dry blending orcompounding an amount of fine mineral matter with particle sizes rangingfrom less than about 50 μm to about 2 μm and a non-biodegradableplastic-based product according to an embodiment of the presentinvention.

In step S22, biodegradable plastic in soil undergoes biodegradation. Thebiodegradation process can be accelerated by inclusion of knownmicrobial nutrients, e.g. poly(hydroxyalkanoates), starches, proteins,which could sustain the plastics conversion process. The extent ofbiodegradation would also depend on the completeness of the oxidativedegradation process and soil conditions (moisture, pH, composition,temperature). The biodegradation process releases the transition metalsin step S23. The released transition metals get bio assimilated in thesoil in step S24 to increase the nutrient availability in soil.

In another embodiment of the present invention shown in FIG. 4, a flowdiagram 4 of a method for remediation of soil is described. Anon-biodegradable plastic-based product in soil is converted into abiodegradable plastic-based product and undergoes biodegradation toremediate the soil. The operating conditions are identical to those ofthe preferred embodiment.

The method for remediation illustrated in flow diagram 4 and as shown inFIG. 4 starts with step S31 where an amount of the fine mineral matterwith particle sizes ranging from less than about 50 μm to about 2 μm isobtained. The fine mineral matter comprises the transition metal fromthe group of Fe, Cu, Mn, Mo, Zn, Co, or combinations thereof to causethe oxidative degradation of the non-biodegradable plastic in soil. Thetransition metals in the fine mineral matter have concentrations definedin the range shown in Table 2.

The fine mineral matter further comprises a promoter from the listconsisting of Ca, K, Mg, or combinations thereof. The promoter in thefine mineral matter has concentrations defined in the range shown in theTable 3.

In step S32, the fine mineral matter is added to the soil directly. Theblending is done preferably with a rototiller or equivalent device toachieve a homogeneous dispersion. A few rototilling soil treatments aredone to promote better dispersion of the fine mineral matter in soil.

In step S33, the non-biodegradable plastic-based product in the blendundergoes oxidative degradation. The transition metals in the finemineral matter act as pro-oxidants and cause oxidative degradation ofthe non-biodegradable plastic-based product to convert thenon-biodegradable plastic-based product into the biodegradableplastic-based product according to Reactions 1, Reactions 2 andReactions 3 of the present invention described above. The promoters inthe fine mineral matter further promotes the oxidative degradation ofthe non-biodegradable plastic-based product into the biodegradableplastic-based product in soil.

In step S34, biodegradable plastic-based product in soil undergoesbiodegradation. The biodegradation process can be accelerated byinclusion of known microbial nutrients, e.g., poly(hydroxyalkanoates),starches, proteins, which could sustain the plastic conversion process.The extent of biodegradation would also depend on the completeness ofthe oxidative degradation process and soil conditions (moisture, pH,composition, temperature). The biodegradation process releases thetransition metals in step S35. The released transition metals get bioassimilated in the soil in step S36 to increase the nutrientavailability in the soil. The bio assimilation of the transition metalsimproves the soil quality and contributes to healthier plants and bettersoil fertility that has been reduced with time.

Method for Remediation of Soil

Another embodiment of the invention involves a method for remediation ofsoil involving a step of obtaining an amount of fine mineral matter withparticle sizes ranging from less than about 50 μm to about 2 μm,comprising a plurality of transition metals, wherein the fine mineralmatter is derived from coal and/or mined from natural resourcesincluding volcanic basalt, glacial rock dust deposits, iron potassiumsilicate and/or sea shore deposits, followed by a step of the finemineral matter with soil to form a blend. The soil contains anon-biodegradable plastic-based product, wherein the plurality oftransition metals cause the oxidative degradation of thenon-biodegradable plastic-based product present in the blend to form abiodegradable plastic-based product, and wherein the biodegradableplastic-based product releases the plurality of transition metals toincrease nutrient availability in the soil. In another embodiment, thenon-biodegradable plastic is a polyolefin. Further, thenon-biodegradable plastic is a hydrocarbon based polymer from the listof polybutenes, polymethylpentenes, polystyrene, styrene/acrylonitrilecopolymers, acrylonitrile/butadiene/styrene terpolymers,acrylate/styrene/acrylonitrile terpolymers, sterene/butadiene/styreneand styrene/isoprene/styrene copolymers, acrylic, vinyl based polymers,polycarbonates, and their mixtures and copolymers, polyesters,polyethers, polyether esters, polyurethanes, polyacetals, polyisoprene,and polybutadiene.

In another embodiment, the fine mineral matter includes a transitionmetal from the group of Fe, Cu, Mn, Mo, Zn, Co, or combinations thereofat the following concentrations:

Fe 14,000 to 45,000 ppm;

Cu 10 to 50 ppm;

Mn 100 to 700 ppm;

Mo 1 to 2 ppm;

Zn 20 to 120 ppm; and

Co 10 to 15 ppm;

wherein ppm are measured with ICP-AES method utilizing nitric acid,hydrochloric acid and hydrogen peroxide in a heated digester.

In another embodiment, the fine mineral matter contains a promoter fromthe group of Ca, K, Mg or combinations thereof at the followingconcentrations:

Ca 1,000 to 18,000 ppm;

K 600 to 4,000 ppm;

Mg 20 to 8,000 ppm; and

alkaline/alkaline earth promoters; and carboxylic acids and/or aminepromoters. In another embodiment, the fine mineral matter furthercontains at least one additive from the group of antioxidants, pigments,IR absorbers, lubricants, unsaturated organic compounds, substitutedbenzophenones, peroxides, biodegradable plasticizers, waxes, UV andthermal stabilizers, biodegradable polymers and oligomers, orcombinations thereof, wherein the antioxidants are used to inhibitoxidative degradation of plastics. In another embodiment, theconcentration of the fine mineral matter in final products ranges fromabout 0.1 to about 3 wt. %. In another embodiment, the fine mineralmatter is added to the non-biodegradable plastic via masterbatches orconcentrates to achieve homogeneous dispersion, wherein theconcentrations of the mineral matter particles in the masterbatches arein the range of about 3 to about 50 wt. %.Method for Treatment of Soil

Another embodiment of the invention includes a method for treatment ofsoil involving adding a biodegradable plastic-based product to the soil,wherein the biodegradable plastic based product is formed by meltblending, dry blending, or compounding a non-biodegradable plastic-basedproduct, and an amount of fine mineral matter with particle sizesranging from less than about 50 μm to about 2 μm, wherein the finemineral matter is derived from coal and/or mined from natural resourcesincluding volcanic basalt, glacial rock dust deposits, iron potassiumsilicate and/or sea shore deposits, and wherein the biodegradableplastic based product releases a plurality of transition metals toincrease nutrient availability in the soil. In another embodiment, thefine mineral matter contains at least one transition metal selected fromthe group of Fe, Cu, Mn, Mo, Zn, Co, or combinations thereof at thefollowing concentrations:

Fe 14,000 to 45,000 ppm;

Cu 10 to 50 ppm;

Mn 100 to 700 ppm;

Mo 1 to 2 ppm;

Zn 20 to 120 ppm; and

Co 10 to 15 ppm;

wherein ppm are measured with ICP-AES method utilizing nitric acid,hydrochloric acid and hydrogen peroxide in a heated digester. In anotherembodiment, the concentration of the fine mineral matter in anon-biodegradable plastic-based product is determined by at least one ofthe factors: the composition of the transition metals, specifics ofsoil, specifics of the non-biodegradable polyolefin resin, climaticconditions and desired useful lifetime of the formulated biodegradableplastic-based product.

In another embodiment, the fine mineral matter includes a promoterselected from the group of Ca, K, Mg or combinations thereof at thefollowing concentrations:

Ca 1,000 to 18,000 ppm;

K 600 to 4,000 ppm;

Mg 20 to 8,000 ppm; and

alkaline/alkaline earth promoters; and carboxylic acids and/or aminepromoters. In another embodiment, the fine mineral matter furthercontains at least one additive selected from antioxidants, pigments, IRabsorbers, lubricants, unsaturated organic compounds, substitutedbenzophenones, peroxides, biodegradable plasticizers, waxes, UV andthermal stabilizers, biodegradable polymers and oligomers, orcombinations thereof, wherein the antioxidants are used to inhibitoxidative degradation of plastics.

One of the advantages of the present invention is that the methodsaccording to the embodiments described utilizes the fine mineral matterto convert the non-biodegradable plastic into the biodegradable plastic.The methods illustrated can be particularly useful in the agriculturalfields. The biodegradable plastic undergoes biodegradation to releasethe transition metals in soil and contributes toward healthier plantgrowth. The invention further finds its application for treatment of thenon-biodegradable plastic waste polluted soil. The utilization of finemineral matter also reduces water contamination that may be caused whenthe coal refuse is discarded as waste and is washed down in the ravines,rivers, lakes, seas, etc. The invention described is simple, easy,economical, environment friendly and efficient in converting thenon-biodegradable plastic into the biodegradable plastic.

From the foregoing disclosure and detailed description of certainembodiments, it is apparent that various modifications, additions andother alternative embodiments are possible without departing from thetrue scope and spirit of the present invention. The embodimentsdiscussed were chosen and described to provide the best illustration ofthe principles of the present invention and its practical applicationsto enable one of ordinary skill in the art to utilize the invention invarious embodiments and with various modifications as are suitable tothe particular use contemplated. All such modifications and variationsare within the scope of the present invention as determined by theappended claims when interpreted in accordance with the benefit to whichthey are fairly, legally, and equitably entitled.

The invention claimed is:
 1. A biodegradable polyolefin compositioncomprising a product of: a non-biodegradable polyolefin-based productand an amount of carbon-free fine mineral matter derived from coaland/or mined from natural resources including volcanic basalt, glacialrock dust deposits, iron potassium silicate and/or sea shore deposits,with particle sizes ranging from less than about 50 μm to about 2 μm,forming a biodegradable polyolefin-based product.
 2. The biodegradablepolyolefin composition according to claim 1, wherein the fine mineralmatter comprises at least one transition metal selected from the groupconsisting of Fe, Cu, Mn, Mo, Zn, Co or combinations thereof at thefollowing concentrations: Fe 14,000 to 45,000 ppm; Cu 10 to 50 ppm; Mn100 to 700 ppm; Mo 1 to 2 ppm; Zn 20 to 120 ppm; and Co 10 to 15 ppm;wherein ppm are measured with ICP-AES method utilizing nitric acid,hydrochloric acid and hydrogen peroxide in a heated digester.
 3. Thebiodegradable polyolefin composition according to claim 1, wherein thefine mineral matter is melt blended, dry blended or compounded with thenon-biodegradable polyolefin based product directly or via masterbatchesor concentrates to achieve homogeneous dispersion, wherein theconcentrations of the mineral matter particles in the masterbatches arein the range of about 3 to 50 wt. %.
 4. The biodegradable polyolefincomposition according to claim 1, wherein the fine mineral mattercomprises of a promoter selected from the alkaline/alkaline earth groupconsisting of Ca, K, Mg or combinations thereof at the followingconcentrations: Ca 1,000 to 18,000 ppm; K 600 to 4,000 ppm; Mg 20 to8,000 ppm; and/or other acidic or amine promoters.
 5. The biodegradablepolyolefin composition according to the claim 1, wherein the finemineral matter comprises at least one additive selected fromantioxidants, pigments, IR absorbers, lubricants, unsaturated organiccompounds, substituted benzophenones, peroxides, biodegradableplasticizers, waxes, UV and thermal stabilizers, biodegradable polymersand oligomers, or combinations thereof, wherein the antioxidants areused to inhibit oxidative degradation of plastics.
 6. The biodegradablepolyolefin composition according to claim 1, wherein the concentrationof the fine mineral matter in the biodegradable polyolefin-based productranges from about 0.1 to about 5 wt. %.
 7. The biodegradable polyolefincomposition according to claim 1, wherein the concentration of the finemineral matter in the non-biodegradable polyolefin-based product isdetermined by at least one of the factors comprising: the composition oftransition metals in the fine mineral matter, specifics of thenon-biodegradable polyolefin resin, climatic conditions and desireduseful lifetime of the formulated biodegradable polyolefin.
 8. A methodaccording to claim 1 of converting a non-biodegradable polyolefinplastic into a biodegradable polyolefin-based product, comprising:obtaining an amount of carbon-free fine mineral matter derived from coaland/or mined from natural resources including volcanic basalt, glacialrock dust deposits, iron potassium silicate and/or sea shore depositswith particle sizes ranging from less than about 50 μm to about 2 μm;and melt blending, dry blending, or compounding the fine mineral matterwith the non-biodegradable plastic to form the biodegradablepolyolefin-based product.
 9. The method according to claim 1, whereinthe non-biodegradable plastic is a hydrocarbon based polymer selectedfrom the list consisting of homopolymers or copolymers or mixtures ofpolyethylene, polypropylene, polybutene, polymethylpentene,polyisobutylene, ethylene propylene copolymers, ethylene propylenerubber, and ethylene propylene diene copolymers.
 10. The methodaccording to claim 8, wherein the fine mineral matter comprises at leastone transition metal selected from the group consisting of Fe, Cu, Mn,Mo, Zn, Co, or combinations thereof at the following concentrations: Fe14,000 to 45,000 ppm; Cu 10 to 50 ppm; Mn 100 to 700 ppm; Mo 1 to 2 ppm;Zn 20 to 120 ppm; and Co 10 to 15 ppm; wherein ppm are measured withICP-AES method utilizing nitric acid, hydrochloric acid and hydrogenperoxide in a heated digester.
 11. The method according to claim 8,wherein the fine mineral matter comprises a promoter selected from thegroup of alkaline/alkaline earth metals consisting of Ca, K, Mg orcombinations thereof at the following concentrations: Ca 1,000 to 18,000ppm; K 600 to 4,000 ppm; Mg 20 to 8,000 ppm; and/or other acidic oramine promoters.
 12. The method according to the claim 8, wherein thefine mineral matter further comprises at least one additive selectedfrom antioxidants, pigments, IR absorbers, lubricants, unsaturatedorganic compounds, substituted benzophenones, peroxides, biodegradableplasticizers, waxes, UV and thermal stabilizers, biodegradable polymersand oligomers, or combinations thereof, wherein the antioxidants areused to inhibit oxidative degradation of plastics.
 13. The methodaccording to claim 8, wherein the concentration of the fine mineralmatter in final products ranges from about 0.1 to about 5 wt. %.
 14. Themethod according to claim 8, wherein the fine mineral matter is added tothe non-biodegradable plastic via masterbatches or concentrates toachieve homogeneous dispersion, wherein the concentrations of themineral matter particles in the masterbatches are in the range of about3 to about 50 wt. %.
 15. The method according to claim 8, wherein thebiodegradable plastic can be converted into at least one of a film, asheet, a fiber, a filament, or a molded form, or combinations thereof.